1. Field of the Invention
This invention relates to a metal modified Beta zeolite for use in fluid catalytic cracking.
2. Description of the Previously Published Art
In the field of fluid catalytic cracking, FCC, the faujasite family of zeolites (synthetic X and Y zeolites) is used to provide high activity high gasoline yield catalysts. Modification of faujasite type zeolites, such as by steam dealumination, allows the refiner to achieve high selectivity for high octane hydrocarbons. This selectivity toward higher octane gasoline is due primarily to an increase in olefins in the gasoline. Although other zeolites, such as ZSM-5 can be added to existing faujasite based FCC catalysts in order to further increase the proportion of high octane hydrocarbons, no zeolite has yet commercially replaced the faujasite zeolites as the major component of an active FCC catalyst.
Zeolite Beta has been shown to be a superior octane enhancing FCC catalyst by G. C. Edwards and A. W. Peters in U.S. Patent Application Ser. No. 842,519, filed Mar. 21, 1986. The higher octane gasoline is again due to a dramatic increase in the olefin content of the gasoline.
D. E. Walsh in U.S. Pat. No. 4,481,104 discloses the use of a modified zeolite Beta in FCC. The modification, which is a strong dealumination, permits good selectivity for distillate production. The patent does not disclose that aromatics can be made with the catalyst.
In another development, A.H.P. Hall in European Patent No. 162,636 discloses the use of gallium loaded zeolites such as ZSM-5 as a way to transform propane and propene into aromatics. T. Mole et al, in Applied Catalysis, volume 17, pages 141-154 (1985) discuss the use of Zn-ZSM-5 as a catalyst in the production of aromatics from propane. Hall and Mole do not discuss, however, the use of Ga or Zn exchanged zeolites in general, and in particular the use of Ga or Zn exchanged Beta in the catalytic cracking of gas-oil or other feedstocks commonly used in FCC.
Plank et al in U.S. Pat. No. 4,157,293 disclose adding zinc to ZSM-5 series zeolites to prepare aromatic compounds from C.sub.2 -C.sub.10 paraffins and olefins. Again, they do not discuss the use of Ga or Zn exchanged zeolites in general, and in particular the use of Ga or Zn exchanged zeolite Beta in the catalytic cracking of gas-oil or other feedstocks commonly used in FCC.
Beta zeolite is a known zeolite which has been described in U.S. Pat. No. 3,308,069. Various metals such as Pd, Pt, Co, Mo, Ni and W have been exchanged with zeolite Beta to produce catalysts for hydroisomerization, hydrocracking, and hydrodewaxing. See U.S. Pat. No. 4,568,655, EP No. 140,608, U.S. Pat. No. 3,923,641 and UK Application No. 2,141,733 A. However, these catalytic reactions are done under completely different conditions than FCC. Beta zeolite can also be used as an adsorbent for the separation of C.sub.9 aromatic isomers. See U.S. Pat. No. 4,554,398.